The present invention relates generally to electron beam deflection structures for electron discharge devices such as cathode-ray tubes, and more particularly to an improved high frequency deflection structure incorporating a slow wave circuit of the meanderline type.
It is well known to incorporate slow wave circuits in electron beam deflection structures for high frequency oscilloscope cathode-ray tubes. Such structures conventionally include a pair of deflection electrodes disposed on opposite sides of the beam path, the electrodes being designed to produce a deflection field that travels along the path in step with the electrons in the beam. The slow wave circuit serves to reduce the deflection signal's travel velocity until it is equal to the velocity of the beam electrons, allowing accurate beam deflection with very high frequency signals.
Prior deflection structures with slow wave circuits include those incorporating helical delay lines, such as the deflectors shown in U.S. Pat. Nos. 3,005,128 to Goldberg et al. and Re. 28,223 to Odenthal et al. While helical deflectors have good performance characteristics, they are relatively complex and expensive to manufacture. Deflectors of a simpler meanderline type are shown in U.S. Pat. Nos. 2,922,074 and 3,174,070 to Moulton and U.S. Pat. No. 3,504,222 to Fukushima.
The meanderline-type deflection structure shown in the Moulton U.S. Pat. No. 2,922,074 includes an elongate slotted deflection plate disposed face-to-face between a pair of similarly-profiled flat metal plates. The deflection plate, which is situated much closer to one of the metal plates than the other, has a plurality of narrow slots projecting inwardly from its opposite edges. The inner ends of the slots overlap to form a plurality of laterally-extending metal strips joined at their outer ends to provide a zigzag path for a deflection signal propagated along the plate. The joined ends of the metal strips terminate in small support tabs, which engage corresponding holes in either of two insulating sheet that support the deflection plate between them. The metal plates are similarly supported between the insulating sheets in suitably spaced relation to the deflection plate, forming a boxlike deflection structure that is mounted within a CRT in a conventional manner. The Moulton U.S. Pat. No. 3,174,070 concerns a similar deflection structure in which a portion of one metal plate is replaced by a section of zigzag deflection plate to provide improved high frequency and transient signal response.
Fukushima describes a class of slow wave structures that include a meanderline of conductive material in the form of a flat serpentine strip. Shielding members are interposed between the loops of the meanderline for the purpose of improving the line's dispersion characteristic. The serpentine strip is mounted above a ground plane in the slow wave structure by means of short pins at the outer ends of its loops. The pins engage holes in insulating plates extending up from the edges of the ground plane. In another embodiment, the meanderline is adhered to the shielding members, which support it above the ground plane. No means for mounting the slow wave structures in a CRT is disclosed.